Sometimes Firefox can corrupt the visited places history database, or places.sqlite. This is a simple way to get almost all of those back:

First, close Firefox, and go to the profile dir, like ~/.mozilla/firefox/xxxxxxxx.slt.
Check that you have places.sqlite, and you should have the old database file as places.sqlite.corrupt. Then do the following:


strings places.sqlite.corrupt | grep ^http | cut -d'"' -f 1 | cut -d"'" -f 1 | sort | uniq | sed -e 's/^/insert into moz_places (url) values("/g' -e 's/$/");/g' | sqlite3 places.sqlite